The present invention relates to separating particulate materials by placing such materials on a porous member while passing gas up through the porous member. One component of the mixture passes down through the porous member, the other component is entrained in the gas flow through the device and transported therefrom.
The mass production techniques used to handle various botanical materials for the manufacture of products using such materials generates a substantial amount of waste. In an industry such as the tobacco industry, where the botanical component of the product is increasingly expensive, there has been a long standing search for a means to separate undesirable components that are unintentionally introduced to the botanical material during handling and manufacture. Due to the significantly different physical properties of botanical materials and such undesirable components such as sand, most separation processes are designed to utilize such differences in properties.
One method of separating the components of such a mixture is to utilize the different absorption characteristics of the two components in a heavy liquid medium. Techniques of this type are somewhat limited in that there must be a subsequent separation of the desired botanical material from the medium effecting the separation. Where the medium carrying out the separation is a liquid, a further consideration must be made as to the effect of the liquid medium on the botanical material. Furthermore, the separation of the botanical material from a liquid may be relatively complex.
U.S. Pat. No. 3,842,978 teaches an apparatus where botanical materials are separated from sand by their different response to a flowing air stream passing through a vibrating array of particles. The separation of the botanical material from the sand in such devices is carried out on a porous array having a flowing stream of gas passing up through the array. Therefore, the separation is primarily controlled by the configuration and packing density of particles comprising the array and the velocity of gas passing therethrough. Use of such prior art devices has resulted in experience whereby the packing density and hence the response of the particles within the array to the vibration changes over a period of time thereby changing the separation performance of the device. There being no practical means of changing the packing of the particles within the array other than physical insertion of particles to the array, the change in operation must be compensated by changes in the velocity of the gas passing through the array or by other relatively ineffective control variables. The physical insertion of particles into the array is disruptive of the separation process requiring the equipment to be partially disassembled.
By contrast, the present invention provides means of changing the density of packing of the particles within the array both to allow compensation for changes in the packing over a period of time and to allow changes in the array necessitated by the introduction of a mixture of botanical materials and undesirable particles of different size characteristics. The nature of the separation process in the specifically cited prior art and the present invention relies on the response of the materials to a flowing air stream. Such a response is dependent on the configuration and size of the particles comprising the mixture. The prior art having no convenient means of altering the packing of the array could not, therefore, be readily adjusted in response to different configurations and sizes of material input. While the gas velocity through the apparatus may be used to make such adjustments, it is interrelated with other characteristics of the device, namely the transport of the botanical materials to a subsequent separating means. The adjustment of the separating process by altering the gas flowing through the apparatus is undesirable.
Therefore, it is the main object of the present invention to separate botanical materials from undesirable particles contained therein whereby changes in the characteristics of the mixtures introduced to the apparatus can be effectively accommodated by adjustments of the porous array carrying out the separation.
A further object of the present invention is to provide a means of adjustment of the separation characteristics of such an apparatus without direct adjustment of the gas flow.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.